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Market-Sized Cutthroat Trout Technical Report Western Regional Aquaculture Center

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Market-Sized Cutthroat Trout Technical Report Western Regional Aquaculture Center Feeds for Production of Market-sized Cutthroat Trout Technical Report WESTERN REGIONAL AQUACULTURE CENTER Gary Fornshell, University of Idaho Christopher Myrick, Colorado State University Madison Powell, University of Idaho Wendy Sealey, United States Fish and Wildlife Service United States Department of Agriculture National Institute of Food and Agriculture 1 PROJECT PARTICIPANTS Christopher Myrick, Colorado State University Cheyenne Owens, Colorado State University Biswamitra Patro, University of Idaho Madison Powell, University of Idaho Pat Blaufuss, University of Idaho Tracy Kennedy, University of Idaho Wendy Sealey, United States Fish and Wildlife Service Brian Ham, United States Fish and Wildlife Service Gary Fornshell, University of Idaho Jeremy Liley, Liley Fisheries, Inc. David Brock, Rangen, Inc. Jackie Zimmerman, Skretting USA Rick Barrows, Aquatic Feed Technologies, LLC Photo credits: Cover: Gary Fornshell Above: iStock.com/KaraGrubis 2 Table of Contents Introduction: Why Consider Cutthroat Trout? 1 Snake River Cutthroat Trout—A Culturable Cutthroat 2 Is Raising Fish for the Recreational Market Worthwhile? 3 Overcoming Challenges to Raising Cutthroat Trout 3 Fish Nutrition 101—A Primer on Feed Formulation 3 Feed Pellet Texture Matters 5 Cutthroat Trout Growth—Does It Match Rainbow Trout? 5 Thermal Growth Coefficient 5 Comparing Rainbow and Cutthroat Trout Performance 6 Suggested Readings 10 Acknowledgments 11 Figures 1. Snake River cutthroat trout. 1 2. Map showing the distribution of extant cutthroat trout 2 subspecies in the western United States. 3. Juvenile Snake River cutthroat trout ready for stocking. 3 4. Classic bell-shaped growth-temperature curve. 6 5. Sigmoid growth curve. Based on Fish Hatchery Management, Second Edition, Gary Wedemeyer, editor 7 6. Market-size Snake River cutthroat trout. 8 7. Growth of Snake River cutthroat trout under production conditions fed two diets. Data points indicate sampling dates. 9 8. Female Snake River cutthroat trout. 10 Tables 1. The two major groups of amino acids. 4 2. Experimental cutthroat trout feed formulation (as-fed basis). 8 3. Calculated constituent values of experimental feed formulation. 9 4. Proximate composition of the diets. 10 Box 1. Calculating Thermal Growth Coefficient 7 3 Photo credit: Wendy Sealey 4 Introduction: Why Consider Cutthroat Trout? Cutthroat trout (Oncorhynchus clarkii) are popular game spawn. Other subspecies of cutthroat trout are adfluvial, fish in the western United States, prized for their brilliant living in large lakes and migrating into rivers to spawn, coloration (Figure 1). For commercial fish farmers, these and still others reside in rivers and streams year-round. colorful trout potentially represent a valuable high-end Cutthroat trout also vary widely in size. One lineage of specialty product for the recreational stocking market Lahontan cutthroat trout currently stocked in Pyramid because of their limited supply compared to the more Lake, Nevada, grows to more than 40 pounds, while some commonly grown rainbow trout (Oncorhynchus mykiss). varieties found in small headwater streams rarely exceed There are a variety of cutthroat trout O.( clarkii) subspecies two pounds. in the western U.S., including at least 11 distinct strains, Despite the wide range of fish sizes and habitats, of which about nine were still present in 1992 (Figure 2) cutthroat trout subspecies share some key characteristics Historical distribution included temperate rainforests of that should be of interest to fish culturists. the Pacific Northwest, pluvial lakes within the Great Basin, • Cutthroat trout are generally spring spawners, a trait subalpine areas of the Rocky Mountains, and high deserts that can increase the likelihood of hybridization with of the Southwest. Inland cutthroat trout have adapted to a most strains of the closely related rainbow trout. diverse range of habitats and are found in tiny headwater • Their natural diet consists mostly of aquatic and streams as well as large rivers and large lakes, such as Lake terrestrial insects and other aquatic invertebrates. Tahoe on the California–Nevada border and Pyramid Lake Larger individuals will eat fish. in Nevada. • Because they are closely related to the rainbow trout, As a result of adapting to diverse habitats, cutthroat cutthroat trout readily interbreed to produce cuttbows, trout display a varied set of life history strategies, a hybrid cross that can sometimes breed successfully. paralleling those seen in the closely related rainbow This propensity to hybridize with rainbow trout is one trout. Some, like the coastal cutthroat trout are similar to of the reasons cutthroat trout declined throughout anadromous salmon, rearing in freshwater as juveniles, their native range following the introduction of migrating into the ocean, and returning to freshwater to rainbow trout. Photo credit: Gary Fornshell Figure 1. Snake River cutthroat trout. 1 • Cutthroat trout, similar to other salmonids, build and as a pure cutthroat trout or more commonly, as a cuttbow. lay their eggs in redds, typically in the gravel The Snake River cutthroat is a popular sportfish, renowned of streams, rivers, or the inlets and outlets of ponds for its willingness to aggressively strike dry flies and small and lakes. Egg incubation time varies with water lures. Fisheries management agencies favor the Snake temperature. River cutthroat because it can be readily distinguished • All cutthroat trout subspecies are excellent sportfish, from other native cutthroat subspecies by its distinct fine- taking flies, lures, and bait. They are often prized by spotted coloration. anglers for their coloration and vigorous fighting Compared to the other cutthroat trout subspecies, ability. the Snake River cutthroat trout is are well suited for commercial aquaculture due to faster growth and better Snake River Cutthroat Trout— feed conversion efficiency. This strain is often approved A Culturable Cutthroat for private aquaculture production and stocking, unlike The Snake River cutthroat trout, a subspecies originally many of the other, rarer, cutthroat subspecies (Figure 3). found in the Snake River drainage, is of particular interest State agencies that regulate aquaculture and the stocking to fish culturists. Its distribution is not shown in Figure 2 of sport fish vary from state to state, as do the nature of because it is the most widely introduced subspecies and the regulations. Consult your state departments of natural has been distributed throughout the western states either resources or agriculture to determine which species are WA MT 10 1 1 Coastal OR ID 2 Rio Grande 11 3 Greenback 7 8 WY 4 Colorado River 6 5 Lahontan 5 9 4 6 Humboldt NV UT 3 CA 7 Alvord CO 8 Whitehorse Bonneville 2 9 10 Westslope AZ 11 Yellowstone NM Figure 2. Map showing the distribution of extant cutthroat trout subspecies in the western United States. Data are from Behnke 1992. The Snake River cutthroat has been widely introduced and is not shown on this map. 2 Photo credit: Gary Fornshell Figure 3. Juvenile Snake River cutthroat trout ready for stocking. approved for propagation, particularly when working with aquaculture industry sales generates $36 in economic cutthroat trout. There are a number of rare subspecies activity, and every million dollars of sales generates that may be subject to special regulations. Alternatively, 500 jobs. contact your state’s extension service for assistance and information. Ultimately, any producer needs to consider Overcoming Challenges to Raising the unique local regulatory environment and economic Cutthroat Trout situation before electing to raise cutthroat trout for the A previous Western Regional Aquaculture Center recreational market. (WRAC) research project evaluated factors limiting consistent growth, survival, and quality from year to year Is Raising Fish for the Recreational of fry and fingerling cutthroat trout production. That Market Worthwhile? project focused on evaluating commercial rainbow trout While the scale of operations that produce trout for the feeds and open-formula experimental feeds, determining recreational market is small compared to that of the fish optimum water temperature and fish rearing density for farms that produce trout for the food market, the economic the best growth. One finding from that study was that contribution of the recreational-based aquaculture sector cutthroat trout were more sensitive to feed ingredients in the western U.S. is substantial. In 2010, about 173 and required different ingredient combinations than the producers of fish for the recreational market generated closely related rainbow trout. $53.2 million in direct annual sales and over 1200 jobs. Their customers included private pond owners, dude Fish Nutrition 101— ranches, fishing clubs, homeowners’ associations, fee- A Primer on Feed Formulation fishing operations, and public waters. The average angler Fish feed typically represents 50% or more of production spent $150 per day at these businesses. In the western costs. Selecting the correct feed is essential for producing U.S., the total annual economic contribution of the aquatic animals economically. Developing cost-effective, recreational-based aquaculture industry was estimated nutritious diets for fish requires incorporating knowledge to be $1.9 billion. Accounting for both forward and of species-specific nutritional requirements into balanced backward linkages, every dollar of recreation-based nutrient-based feeds that are delivered using appropriate
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